Peavey CS-900 User Manual

There are $everal valid exceptions to the full clockwise rule. The tirst one presented her© involves large systems where It is often necessary
to employ many power amolifiers to supply the same signal to multiple speaker systems to achieve the necessary sound pressure levels or
audiencecoverage. It the various poweramplltiers have different sensitivity ratingaandyorthevariousloudspeakerenclosures have different
efficient ratings, then Itmightbe necessary toadjusi certain sensitivity controls to achievea balanced sound pressure level between the parts
of the system, in tni$ case, the loudest amplifter/speaker combinations will require those amplifier sensitivity controls to be adjusted
counter-clockwise as nesessary. Often in such systems, both Peavey and non-Peavey power amplifiers might be employed. In this case, as a
starting point,itmight be necessary to match the sensitivity ratingofthe Peavey power amplifier to that of the competitive poweramplitier. As
anexample, several competitive power amplifiers onthe market haveasensttivlty rating of2voits RMS (that’s+6 dBV as readfrom the CS-900
sensitivity control clock). If such a competitive amplifier is used with the CS-900, then the CS-900 must be set to +6 dBV. A second valid
exception to the rule might occur whenever a biamp system is used. This exception will be discussed later in this manual when blamped
systems are presented, A third valid exception Is involved in amall club, church and studio applications, where the full power output
capability of the power amplifier is not needed orthere is no requirement for large amounts of headroom capability. Simultaneously, these
applications usually requireavery low noise system. In this case, ltl$ possible to reduce the overall system noise altheexpenseof headroom
capability by increasing the power amplifier sensitivity accordingly. As an example, if instead of a sensitivity rating of *3 dBV, we adjust the
CS-900 to a rating of+10 dBV, overall system noise will improved by 7 dS with the resulting 7 dB decrease in system headroom. Remember,
oncethts is done, themixer operator cannot reestablish full headroom performance sett Ingsalthe mixer. Ifhe wantsthis headroom back, he
must do it by resetting the power amplifier sensitivity.
LED ARRAYS (2)
The CS'900hasatrtcolored LED array on each Channel toindicate output power level, Thearray is calibrated In two different waystooffer
maximumflexibility as to usage. To the left of each array, the calibration is percent of full power output. Thetop LED, labeled 100%, will flash
when the CS-900 has reached full RMS power output (450 watts RMS) on that respective channel. Operation at power output levels below
100% will naturally be indicated by lower LED readings. The lowest value indicated lsO.4% of full power, which corresponds to 2.4 watts RMS
output. Operation below that power level will not be Indicated since the lowest LED Is calibrated at 0% or standby. This LED should be
illuminated whenever the amplifier Is operating with AC mains power applied under zero signal conditions. To the right of each array, the
calibration is 'dB belowfull power/'This is a very convenient scale which Indicates the amount of power amp headroom left lor any signal
condition. On this scale, the lowest LED is labeled "V (infinity), which is consistent with the dB system. If fault conditions exist, such as a
hjghtemp. thermal shutdown or a DC offset at the output (caused bytheamplltieritself orexternally Induced atthe input), thIsLED will go off
and remain off until thefault isdeared. You will also notice tnatthis LED will not llghtfor approximately two seconds during the power-up
sequence, and will go off very quickly during the power-down sequence. This is normal. Indicating that the transient protection circuitry is
operating properly. Should this LED everfall to lightafterthe normal power-upsequence, and no otherfaultconditions exist, tnenthemains
AC powerlothatchannel might not be applied. Such acondition might bea blown fuse in that associated channel. If upon replacing the fuse
(with ihssametypeand rating) It does not clear the problem, then the amplifier will require servicing by a qualified service technician. Since
the CS-9DC is a redundant two-channel amplifier, operation of the working channel Is unaffected by the down channel and continued
operation under these circumstances will in no way harm the amplifier and is considered normal operation.
OOT^ COMPRESSION
The CS-900 Is a compact and powerful amoHtierthatfeatures a newtype of dynamic compression. This compression system enables the
userto maximize The performance oflheampllfler/speakercombination. We havedeterminedthrough much research thatthecompression
clrcuitryshouldpreventthepowerampilfierfromrunnlngoutof headroom (clipping) and should beas simple to operate as possible to avoid
unduecompkcalionfortneuser.Thiscoinpression system Is activated by our exclusive DDT compression circuitry that senses conditions
that might overload the amplifier and activates compression when clipping Is imminent. In other words, compression lakes place whenever
signal conditions exist which prevent the amplifiers from faithfully reproducing the input signal Threshold then is clipping itself and no
specific Ihresholdconlrol Is provided. This techniqueeffectively utilizes every precious wattavailabiefrom the powerampllfler.Techniques
using external compressors and limiters are usually leas effective, limit output power levels and require additional controls, which add
comp lexi ty to an already complicated system. The DDTsy stem is an automatic, hands-offapproachtotheproblemofampcllpping. Because
of the dynamics of music and vocals, it is quite common to activate the DDT compression circuitry almost constantly during a high level
performance since this was what h Is designed to do; i.e., to maximize the dynamics available from the amplifier within its power output
capabilities regardless of power suppty/AC line voltage variations and load imc>edance selection.
DDT' ACTIVE LED S (3)
The DDT actIveLED's Indicate when compression Is taking place. As long as gain reduction is occurring, the LEO will continue to fight,
thereby giving a valuable Indication of this unique compression function. The DDT function can be defeated on both channels
simultaneously by selecting the defeat position on the DDT compression switch (7) located onthe back panel of the CS-900. When the
CO mpressoris defeated, the DDT active LED now Indicates dipping, the condition where the amplifier Is failing to faithfully reproduce the
Input signal. Defeating the DDT compressor should not betake lightly or simply as a matter of course. Most loudspeaker systems simply
can not handle the square wave power of the CS-900 and defeating this valuable II mlt is only asking fortrouble In the long run. Often studio
engineers feel the need to defeat the DDT compressor for fear that It might color the sound In studio listening Occasionally, external
compressors/llmltersare employedtoautomaticallyeetthe level of a particular system and thus, The unkncwningtechniclan will defearthe
DDT compressor thinking It is not needed. Those are examples of not understanding the operation of the DDT circuitry. The DDT
compressor isonlyactivated when clipping is Imminent. Until this occurs, rt’seimply a passive friend. The only reason that the defeat swttch
Is there m the first place Is to allow check-out and service technicians to evaluate the power amplifier at clipping. Valuable performance
information, such as nppie and regulation, can only be assessed when an amplifier is allowed to clip. Other than those times, we strongly
suggest that the DDT compressor switch be set m the active position and left that way.
THERMAL SYSTEM
The CS-900 has a unique thermal system that employs a tunnel-like heat sink design to provide maximum cooling for the 32 power
transistors(16loreachchannei). A single 120 CFM Ian mounted on the back panel of the amplifier provides an almost unrestricted airflow
through thetunnel to providethe lowest possibleoperailngiemperalureforthepowerdevices. This approach is so efficient that even music
power operation into 2 ohms will rot cause a thermal shtudown unless the ambient air temperature is considerably higher than normal
(above 40® C}. Under normal intermittent applications, low speed fan operation wiW provide adequate cooling. Since the CS-900 s a
redundanttwo-channelamplifier, but only one fan isemployed, the fan circuitry Is an independent system, separately fused Internally. You
will notice that the heat sink com ponentsaredivided horizontally. The lower half contains Channel A output transistors, while the upper half
belongs to Channel B. The fan naturally provides equal cooling for both channels. Each channel has a separate built-in thermal sensor and
separate logic circuitry. If one channel heat sink reaches an operating temperature of 60® C, then its logic will cause high-speed fan
operation regard less of The other channel's operating temperature. In other words, either channel heating will control the fan speed. Under
normal continuous usage at full-rated power output Into the rated load, the lherrT>al logic system will continuously monitor heat sink
lemporafures and will automatically select the tan speed required to maintain safe operating limits for the power irenslstore.

Peavey CS-900 Specifications

General

Brand	Peavey
Model	CS-900
Category	Amplifier
Language	English